How to break in a new fuel injected engine?

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Mopar87

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Currently the engine in my 73 scamp is destroyed.The car sat for 10 years before I got it, but water got into the engine and rusted everything together so its 318 is junk.I have a 318 that came from a 78 truck that should run sitting in my garage that I was planning on throwing in it until I can build an engine for it.The plan is a fairly hot 5.2L magnum thats been zero decked with kb167 pistons,a stout cam, and some pretty agressive headwork.Intake manifold will be a Mopar M1,and it will breath through a set of 1 3/4" long tube headers.The problem is it will be running fuel injection.I've heard that you should break in an engine how it will be driven and I plan to drive this one pretty hard.I've also heard that you should attempt to start the engine on the stock engine management and run it gently for 10 miles and a few heat cycles before getting it tuned.I dont know if the stock computer could even figure out how to fire this beast let alone run it well enough to make it 10 miles without melting a piston. Stock fuel injectors are 23-24 lbs-hour and according to an online calculator I would need atleast 31 lb injectors minimum.So what would be the best way break in the engine and get it running at least well enough to a tune on it?Should I slap on the stock keg manifold during the break in to keep the computer from commiting suicide?
 
If you want to use the full potential of that setup you may as well get a tunable ECU
 
New engine and unknown fuel system is a tough situation. It'll fire it up on the stock system, but how things will behave even idling is the big question. With a cam in this thing disrupting manifold pressure vs a stockish cam, I would expect the stock FI system to be somewhat whacked out so that's a crapshoot with a biggish cam. I don't see how just changing intake manifolds will make any difference to the cam situation. Maybe someone has tried it here and can attest to the results and say what cam they had.

Do you have a known running carb and intake set-up, and a stock distributor and ignition system? I'd use that for the initial cam break-in so you can get through that most critical phase without starting and stopping the engine. (Once you are through that, then all that is left is maybe some final ring/bore wear-in.) You could even do some heat cycles and driving around on that setup 'til you get the EFI system ready.

If you're gonna drive around on an unknown tuning setup of any type, I'd want to have an AFR gauge on it to keep an eye on the mixture. So you ought to consider adding one, IMHO. (Just keep in mind that they will read abnormally lean during the first few minutes of engine warm-up.)

BTW, that lbs per hour limit on the stock injectors will mostly come into play at moderate throttle or WOT. FWIW, if your new setup will have an adjustable fuel pressure regulator, you can play with fuel pressure adjustments to compensate somewhat for that.
 
If your question is how to break in a new engine the protocol is the same as any other . It must start right away andrun up to 2500rpm for 20 minutes , shut down to dead cold and repeat . That's if you have a LA 318 . If you have a 5.2magnum you just have to seat the rings by running engine up and down the rpm scale for about 20 minutes and repeat . So I don't really know what the issue is.
 
You're right.... I was thinking only of the flat tappet cam world for the cam break-in part. So probably a non-issue... depending on what cam type the OP is using.

But I'd expect a stock FI ECU with low/erratic manifold pressure around idle and at low RPM part throttle, due to any largish cam, is gonna misadjust the mixture. And an unknown new FI map is anyone's guess. That's the issue, as I understand it.
 
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What efi system? There are forums for those, ask there. I got a Sniper, good info on Facebook group. Someone’s done it before somewhere
 
The stock ECU is gonna be scratching its head over the MAP as your new cam will be pulling ~12" instead of >19" so it will be dumping fuel. making it rich. Your O2 will be like WTF and will be cutting fuel to clean it up. its a vicious cycle...Id run a stock jetted carb with nothing but the ignition hooked up for the cam break in. The 'running the motor like you want to drive it' would pertain to a learning ECU like an EECIV or something a little more flexible than a Mopar ECU. If you dont have that option. get it to start and run to 2000 RPM, and hold it there while watching your AFR. It may be enough RPM to get the ECU to play nice and give it an acceptable afr. If your running a roller, then dont worry about cam, worry about your ECU keeping up with the strange demands of a non stock cam. MS it!
 
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The stock ECU is gonna be scratching its head over the MAP as your new cam will be pulling ~12" instead of >19" so it will be dumping fuel. making it rich. Your O2 will be like WTF and will be cutting fuel to clean it up. its a vicious cycle...Id run a stock jetted carb with nothing but the ignition hooked up for the cam break in. The 'running the motor like you want to drive it' would pertain to a learning ECU like an EECIV or something a little more flexible than a Mopar ECU. If you dont have that option. get it to start and run to 2000 RPM, and hold it there while watching your AFR. It may be enough RPM to get the ECU to play nice and give it an acceptable afr. If your running a roller, then dont worry about cam, worry about your ECU keeping up with the strange demands of a non stock cam. MS it!
Cam will be a full roller,seems strange to want to even consider a flat tappet cam when the engine comes stock with a roller cam. I watched an episode of engine master's back when it was free and they were comparing carbed and fuel injected engines and they couldnt get the fuel injected engine to run on a carb manifold because the vacuum signals were weird so they put a single plane intake on it,and it ran fine. I'm kinda interested in the stock cheby ls engine management because supposedly its pretty adjustable and swap friendly.Eventually ,I would like to get rid of the distributor and run a coil near plug ignition system for the hotter and more precise spark.That is a lofty goal but I should probally take it all in stages rather than building it like that first because then it will never get done..
 
great idea, take one phase at a time. Not sure how the magnum got its CPS but a jeep CPS is like a drop in distributor that will do what you need it to do oil pump wise. Of course an electronic distributor with 7 of 8 vanes ground off will do it too for sequential EFI. No need for a cap, rotor or plug wires if going the COP or CNP ignition setup. Just a nice snap on cover.
 
Here's the jeep cam position sensor I'm using on my small block, think it was cnc motorsports was the company that made them, or just google search CPS adapter for small block and it should pop up. But I have the set up cop and fuel injection. Still finishing up some things haven't fired it yet, but I'm also using megasquirt. If you use the factory harness look at a AEM programmable ECU for it, they probably have one that will work for the 5.2.

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I think there's a few guys on the web I've found that can reflash the Dodge stock ECU, but to be honest if you want the option of tuning down the road. I'd look at doing a ECU that you can tune. Are you wanting full sequential control or will batch fire be sufficient?
 
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